NASA is going back to the Moon! We’ll follow the crew of Artemis II every step of the way.
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Post-Failure Autopsy And Analysis Of An LFP Battery
Recently [Kerry Wong] had one of his Cyclenbatt LiFePO4 batteries die after only a few dozen cycles, with a normal voltage still present on the terminals. One of the symptoms was that as soon as you try to charge it, the voltage goes up very rapidly to above 14 V due to what appears to be high internal resistance, and vice versa for discharging. In addition, the Bluetooth feature of the BMS appeared to have died as well, making non-invasive diagnostics somewhat tricky.
After gently cutting open the plastic case, [Kerry] was greeted by the happily blinking blue LED of the Bluetooth module and deepening the mystery. Overall the build quality looks to be pretty good, with no loose cables as seen with certain other LFP batteries.
Cell voltages measured normal, with no significant imbalance. Next was measuring the internal resistance, which showed a clear issue. One of the cells was reading over 3 Ohms, whereas the others were in the milli-Ohm range. This would definitely explain the issues with charging and discharging, with a single bad cell causing most of the issues.
Of course, why the Bluetooth feature failed remains a mystery, and there’s still a lingering question on whether the BMS practiced proper balancing between the cells, as this can also cause issues over time.
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Every 3D Printable Film Camera, In One Place
For those of us who hack old cameras, the 3D printer has undoubtedly been a boon. High precision, or at least consistent precision, lightproof enclosures can be easily made and reproduced for others. As a result there are quite a few printable cameras out there, and we’ve featured our share here. We didn’t realize just how many there are without the work of [Sebastian] though, as he’s gathered together every one he can find in a glorious catalog of homemade photographic construction.
As a snapshot of the world of home made cameras it’s refreshing to see such a wide range of designs. There are pinholes aplenty as well as cameras using lenses from scavanged point and shoots through 35mm SLR, medium format, and even one using a Micro Four Thirds compact digital camera lens. For film there’s 35mm and 120 as well as large format, but we’re pleased to see a few instant cameras in there. Some of the models in the list are paid-for designs but most of them are free, so you probably won’t need any encouragement to make yourself a camera!
Unless we missed something, we didn’t see any movie cameras in the list. With 35mm and 16mm models to be found, we hope some of them make it.
Watch An Electro-Permanent Magnet In Action
Electro-permanent magnets (EPMs) are pretty nifty concepts, and if you aren’t familiar with them, they are permanent magnets with the ability to be electrically switched on or off. Unlike an electromagnet — which maintains a magnetic field only while power is applied — an EPM can remain “on” even when power is removed. Want to see one work? There’s a video embedded below that shows one off, but if you’d like to know how they work, we have you covered.
Inside are two types of magnet, one of which is permanent and the other being a semi-hard magnet paired with an electromagnetic coil. A semi-hard magnet’s flux can be changed by exposing it to a strong enough magnetic field, and that’s the key to making it work.
When both magnets work together, the EPM is “on” and acts like a permanent magnet. To turn the EPM off, the polarity of the semi-hard magnet is flipped with a short and powerful electromagnetic pulse, after which the two magnets oppose one another and more or less cancel each other out. So rather than generating a magnetic field, an EPM more accurately reconfigures it.
As intriguing as EPMs are, we haven’t really seen one properly in action until it was brought to our attention that [Dave Jones] of EEVblog tried one out last year. He received a Zubax FluxGrip EPM, which is intended for drone and robotic applications and can hold up to 25 kg. Watch [Dave] fire it up in the video (link is cued up to the 7:30 mark), it’s pretty interesting to see one of these actually work.
EPMs are not prohibitively expensive but they are not exactly cheap, either. But if a switchable magnet sounds up your alley and you can’t afford an EPM, consider an alternative “switchable” magnet design that works by momentarily canceling out a permanent magnet with a paired electromagnet. Unlike an EPM, it’s not a permanent switch but it would be enough to drop a payload.
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OldVersion Is Back, And Better Than Ever
You know what they say — you can’t keep a good website down. OldVersion.com, the repository of outdated software that has been serving up old versions of tools you need for the last twenty-five years, is not going away as we reported last year. Not only is it sticking around, it’s gotten a retro facelift inspired by Windows 3.1 or OS/2. Mostly Windows, given the screensaver, but we’ll let you find that for yourself.
We’re thrilled to see that OldVersion has gotten the support they need to keep going after running into financial troubles. According to founder Alex Levine, some of that support came as a result of the Hackaday article reporting on the then-upcoming closure, so kudos to you guys for stepping up.
While we absolutely love the retro redesign of the new website, that’s one thing notably lacking — an obvious donation button. Well, that and old-school HTTP support so you can get on with your retromachines, but that, at least, is in the works according to the site roadmap. It’s a little weird that in this year of the common era 2026 you have to do extra work to give up on HTTPS functionality, but it is the way it is.
In the meantime, the site is fully usable as long as you have HTTPS capability, or go through a proxy. Perhaps you could use this ESP8266 code to get started making one, if you don’t want to embarrass your old computer by using something more powerful than it as a pass-through.
Speaking of proxies, if old versions of software aren’t enough for you, how about an old version of the internet? We heard you like old versions, so you can visit an old version of OldVersion!
Note that if you’re reading this after 01/04/2026, the look-and-feel of OldVersion.com may not match what’s depicted here.
Battery Tester Outperforms Cheaper Options
Batteries are notoriously difficult pieces of technology to deal with reliably. They often need specific temperatures, charge rates, can’t tolerate physical shocks or damage, and can fail catastrophically if all of their finicky needs aren’t met. And, adding insult to injury, for many chemistries, the voltage does not correlate to state of charge in meaningful ways. Battery testers take many efforts to mitigate these challenges, but often miss the mark for those who need high fidelity in their measurements. For that reason, [LiamTronix] built their own.
The main problem with the cheaper battery testers, at least for [LiamTronix]’s use cases, is that he has plenty of batteries that are too large to practically test on the low-current devices, or which have internal battery management systems (BMS) which can’t connect to these testers. The first circuit he built to help solve these issues is based on a shunt resistor, which lets a smaller IC chip monitor a much larger current by looking at voltage drop across a resistor with a small resistance value. The Pi uses a Python script which monitors the current draw over the course of the test and outputs the result on a handy graph.
This circuit worked well enough for smaller batteries, but for his larger batteries like the 72V one he built for his electric tractor, these methods could draw far too much power to be safe. So from there he built a much more robust circuit which uses four MOSFETs as part of four constant current sources to sink and measure the current from the battery. A Pi Zero monitors the voltage and current from the battery, and also turns on some fans pointed at the MOSFETs’ heat sink to keep them from overheating. The system can be configured to work for different batteries and different current draw rates, making it much more capable than anything off the shelf.
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Mercury Audio Cables, So Nobody Else Has To Do It
We’ve seen our fair share of audiophile tomfoolery here at Hackaday, and we’ve even poked fun at a few of them over the years. Perhaps one of the most outrageously over the top that we’ve so far seen comes from [Pierogi Engineering] who, we’ll grant you not in a spirit of audiophile expectation, has made a set of speaker interconnects using liquid mercury.
In terms of construction they’re transparent tubes filled with mercury and capped off with 4 mm plugs as you might expect. We hear them compared with copper cables and from where we’re sitting we can’t tell any difference, but as we’ve said in the past, the only metrics that matter in this field come from an audio analyzer.
But that’s not what we take away from the video below the break. Being honest for a minute, there was a discussion among Hackaday editors as to whether or not we should feature this story. He’s handling significant quantities of mercury, and it’s probably not over reacting to express concerns about his procedures. We wouldn’t handle mercury like that, and we’d suggest that unless you want to turn your home into a Superfund site, you shouldn’t either. But now someone has, so at least there’s no need for anyone else to answer the question as to whether mercury makes a good interconnect.
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